GitLab

Update clang_version from 7.0.0 to 8.0.0 and remove the code to remove
the old library directory.

Remove the _LIBCPP_HIDE_FROM_ABI define, it is no longer needed.

R=hans@chromium.org,thakis@chromium.org

Bug: 871418, 872926
Change-Id: Ibf6734500aa75a349fa772b225b8b15fddfe3661
Reviewed-on: https://chromium-review.googlesource.com/1194698Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587602}